Personality disorders are common in the general population and are particularly prevalent among psychiatric patients. Of concern, personality disorders are associated with a number of adverse outcomes, including suicidality, attenuated treatment response, increased utilization of health care services, and significant functional impairment. It is therefore crucial that clinicians and researchers have tools available to efficiently assess this key aspect of psychological functioning. Unfortunately, many common measures of personality pathology are quite long and inefficient and/or must be administered and scored by professional staff. Moreover, a number of categorical and dimensional models of personality pathology have been proposed, but the lack of integration and comprehensiveness among these models has led to confusion in health care and research settings and has resulted in a decrease in assessment of personality pathology. Thus, in the proposed research, our general aims are to (a) identify a comprehensive and integrative set of dimensions relevant to personality pathology, and (b) develop an efficient computerized adaptive method the CAT-PD to measure these dimensions. Computerized adaptive tests (CATs) are rooted in modern psychometric methods and are designed to select items for administration that are tailored individually to each patient, which typically leads to significant gains in measurement efficiency with little or no cost to test reliability or validity. To accomplish our general goals, we plan a five-phase project in which we (Phase 1) identify the content domains to be assessed and develop the initial item pool based on the public domain International Personality Item Pool (IPIP), (Phase 2) collect self-report item responses from two samples each of psychiatric patients (total N = 500) and community-dwelling adults (total N = 500) and conduct analyses of those responses to develop and cross-validate the CAT-PD scales, (Phase 3) calibrate the CAT-PD items using item response theory (IRT) and conduct CAT simulations to guide construction of the live CAT-PD software, (Phase 4) develop CAT-PD software based on the results of all previous phases, and (Phase 5) conduct a live-testing study of the CAT-PD in a new sample of psychiatric patients (N = 300) to study its efficiency and construct validity and establish cut points and scoring rules designed to increase the tool's practical utility across a wide variety of applied and research settings. It is our hope that the proposed research will help to integrate the numerous dimensional models of personality pathology, yield a comprehensive set and efficient measure of personality disorder dimensions, and contribute to advancements in personality disorder theory, research, diagnosis, and intervention. PUBLIC HEALTH RELEVANCE: Because personality disorders are common in the general population and are associated with a number of adverse outcomes, including suicidality, attenuated treatment response, increased utilization of health care services, and significant functional impairment, the proposed project is relevant to public health. It is crucial that clinicians and researchers have tools available to efficiently assess this key aspect of psychological functioning. The proposed research will help to integrate the numerous models of personality pathology, yield a comprehensive set and efficient measure of personality disorder dimensions, and contribute to advancements in personality disorder theory, research, diagnosis, and intervention.